The isolation of individual colonies of micro-organisms (and in particular bacteria) is an important procedure in many microbiological laboratories. This isolation of bacteria is normally done either manually by skilled laboratory technologist or automatically by robotic streaking equipment. In either case, a microbiological sample is first dispensed upon the surface of a solid culture medium followed by the spreading of the microbiological sample across the surface of the medium (called “streaking”). Typically, multiple streaks are made of increasing dilution of the inoculum across the solid culture medium.
The streaks of increasing dilution tend to provide, generally towards the tail of the streaks, a number of single cells that allow for the growth of isolated microbiological colonies after incubation. These isolated colonies may then be analysed for various physical features e.g. colony morphology, and may undergo staining and other procedures which may be necessary for determining, for example, the genus, the species and/or the strain of the previously unidentified organism in the microbiological sample.
Traditionally, this analysis has been carried out visually in a microbiological laboratory by skilled technologists, resulting in the technologist making a microbiological assessment. This assessment may include the detection of the presence or absence of bacterial colonies, the detection of colour(s) of each colony type, the mapping of colour distribution to determine the presence of variations in colour which could be attributed to fermentation or haemolysis, the differentiation between confluent and isolated colony growth, the measurement of colony texture or viscosity, and the determination of two-dimensional and three-dimensional shape, and/or enumeration of the different types of colonies.
Where growth of potentially pathogenic bacteria is identified, the solid culture medium is progressed to the next step of the laboratory workflow and becomes the subject of further confirmatory identification and antibiotic susceptibility testing, in line with current regulatory requirements.
Over the years, there has been some efforts, for example, to capture images (either still or video, and in either analogue or digital forms) of bacterial colonies so that the technologist is able to more efficiently view a higher number of surfaces using visual aids such as monitors, microscopes, colony counters and/or computers.
It is important that these images are captured accurately, as the colour, shape and texture of the bacterial colonies, and the colour of the solid culture medium are used in identifying, for example, the bacteria type. Many commercial solid culture mediums, such as agars, are initially of various colours and transparencies and some are almost totally opaque (e.g. Methicillin-Resistant Staphylococcus aureus (MRSA) identification agars). Some plates are split into two halves, so that each side of the plate has a different type (and potentially colour) of agar. Also, the bacterial colonies can be of different colours, shapes and textures. Some are simple round spots, others swarm in continuous waves across the agar surface and some have characteristic surface topography such as dimples or a granular texture. The effect of the bacterial colonies on the colour indicators blended in the agar formulation can, for example, produce a strong colour reaction, such as blue halo around colonies of MRSA on specific indicator agar or colour reaction resulting from pH changes caused by bacterial growth on agar containing appropriate indicator compounds, such as neutral red. In another example, further colour changes are visible in blood agars, immediately below and around colonies which are able to damage or destroy red blood cells via haemolysis.
It is an aim of the present invention to provide an apparatus for capturing sufficiently accurate images of microbial growth in order to assist in providing a microbiological assessment.
Before turning to a summary of the present invention, it must be appreciated that the above description of the prior art has been provided merely as background to explain the context of the invention. It is not to be taken as an admission that any of the material referred to was published or known, or was a part of the common general knowledge in Australia or elsewhere.